Allow whitespace before protocols.
Release 3.0.4.
Update Travis version matrix.

- Temporarily removed 1.9.2 because Travis is having trouble installing
  Nokogiri.

- Replaced 2.1.2 with 2.1.5.
Merge branch 'master' into dev-3.1.0

Conflicts:
	HISTORY.md
	lib/sanitize/version.rb